I. Field of the Invention
The invention relates to an angle sensor which reacts to a magnetic encoder.
II. Technical Background
In such angle sensors, the rotation angle transmission between the encoder, thus the magnet, and the sensor element in the angle sensor, which is typically configured in the form of an electronic chip (IC), is exclusively performed by magnetic field lines and, in particular, without mechanical coupling, so that the sensor element and, in particular the entire angle sensor, can be completely encased and disposed in a space of its own, as long as it is thus assured that the magnetic field of the encoder magnet can penetrate into the space up to the sensor element.
For sensor elements, elements are being used which operate according to the “Hall-principle” or according to the magneto-resistive principle.
In the state-of-the art angle sensors are known in which the sensor element in the form of an IC and additional electrical components used for processing the signals of the IC are jointly disposed on a circuit board, and the entire circuit is disposed in a surrounding housing.
Depending on the application, thus prevailing environmental conditions, different partially contrarian objectives have to be accomplished.
On one hand, the housing shall be configured as mechanically stable as possible and therefore shall be made of metal.
On the other hand, the housing has to be shielded against interference effects from magnetic fields which do not originate from the encoder magnet, wherein a magnetic shielding made of iron is preferred.
The angle sensor shall be produce in the most cost effective manner and, thus, shall be configured as simple as possible.
Furthermore, the electronics have to be protected against the penetration of moisture, which would always lead to a defect of the sensor element medium term. Thus, the greatest risk does not come from a surge of moisture but from moisture slowly penetrating due to capillary effects e.g. through the strands of the cables connected to the electronics and leading to the outside, the so called “longitudinal water”.
With respect to these conflicting requirements, there are currently two different embodiments available on the market:
On the one hand, there are angle sensors in which the entire electronics are mechanically well protected in a mostly pot-shaped metal housing and well protected against penetrating moisture. However, the metal housing and its sealing cause manufacturing complexity and, thus, high cost.
On the other hand, there are angle sensors in which the electronics are directly mounted to the circuit board which is bolted down at the place of installation. The electronics are only protected by a plastic cap in a basic manner against mechanical damage and are not sealed against moisture at all.